Sorbs will remove you from their list once you contact them and prove you have a static IP address though.
When my company moved buildings we went to a new ISP and was assigned a static address that was previously part of the ISP's dynamic pool.
The reverse resolve for it was 203.161.88.182.dynamic.amnet.net.au.
Once I contacted our ISP and had it changed to 203.161.88.182.static.amnet.net.au. and then contacted sorbs they removed us from the list.
Just go to the Sorbs web site and follow their instructions.
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Jim Barber
DDI Health